Turbochargers may be used in engines to increase the power output of the engine for a given displacement as compared to a naturally aspirated engine. It may be desirable to decrease the flow path between the turbine in the turbocharger and the combustion chambers by positioning the turbine close to the exhaust ports of the cylinders. Such positioning decreases losses in the exhaust gas flow, thereby enabling the speed of the turbine to increase. The increased turbine speed increases the amount of compression provided by the compressor. As a result, the power output of the engine may be increased.
However, due to the proximity of the turbine to the combustion chamber, the turbine and surrounding components may experience elevated temperatures. In some engines the exhaust manifold and turbine housing may have radiating surface temperatures over 900° C. Consequently, the turbine and surrounding components, such as a wastegate and an actuator of the wastegate, may experience thermal degradation, thus decreasing component longevity. For example, an electrically actuated wastegate (EAWG) may become inoperable at higher temperatures due to temperature-sensitive control components included therein. As an example, a wastegate actuator and its circuitry may significantly degrade at elevated temperatures affecting wastegate control and engine performance.
An example approach to cooling a wastegate actuator is shown by Matthews in US 2014/0047832. Herein, the wastegate actuator receives cooling air via a conduit from upstream of an intake compressor. However, the inventors herein have recognized a potential issue with the example approach shown by Matthews. As an example, intake airflow may be insufficient to cool the wastegate actuator during certain engine conditions. During boosted conditions, a substantial portion of intake airflow may be drawn into the intake compressor for combustion while a significantly smaller portion of intake airflow may enter the conduit towards the wastegate actuator. Accordingly, the wastegate actuator may not be cooled adequately resulting in an increased likelihood of thermal degradation.
One approach that at least partially addresses the above issue includes an example system for a vehicle, comprising a radiator fan at a front end of a vehicle, an engine coupled to an exhaust passage, a turbine positioned in the exhaust passage, a bypass conduit in fluidic communication with a turbine inlet and a turbine outlet, a wastegate positioned in the bypass conduit, and a wastegate actuator adjusting a position of the wastegate, the wastegate actuator receiving airflow from downstream of the radiator fan via a cooling duct. In this way, the wastegate may be cooled during different engine conditions by air received via the cooling duct from the radiator fan.
Another example approach includes a method for a boosted engine in a vehicle, comprising adjusting each of a speed of a radiator fan and a position of grille shutters of the vehicle responsive to a temperature at a wastegate exceeding a temperature threshold. Thus, the radiator fan and grille shutters may facilitate cooling of the wastegate (and a wastegate actuator).
For example, a boosted engine in a vehicle may include an intake compressor driven by an exhaust turbine. A wastegate may be positioned in a bypass conduit coupled across the exhaust turbine. As such, a position of the wastegate may be adjusted by a wastegate actuator based on a desired flow of exhaust gases across the exhaust turbine. The wastegate actuator (and the wastegate) may receive cooling airflow from a front of the vehicle via a cooling duct. Specifically, a first end of the cooling duct may receive airflow from downstream of each of a radiator fan and grille shutters, and transfer the airflow via a second end of the cooling duct to the wastegate actuator (and the wastegate). Further still, a speed of the radiator fan and a position of the grille shutters may be adjusted in response to a temperature of the wastegate, and the wastegate actuator. When an estimated temperature of the wastegate (and the wastegate actuator) exceeds a temperature threshold, the speed of the radiator fan and/or the position of the grille shutters may be varied to provide cooling airflow via the cooling duct to the wastegate and wastegate actuator.
In this way, a wastegate and a wastegate actuator may be cooled to reduce component degradation. By using airflow from the radiator fan and grille shutters, the wastegate actuator may be cooled when desired. Further, airflow directed towards the wastegate actuator may not depend on existing engine conditions. As such, the radiator fan may be actuated in response to heating of the wastegate and may not be based on other engine parameters. Thermal stress on the wastegate may be reduced by the cooling airflow enabling an increase in the longevity of the wastegate and wastegate actuator. The air flow received from the radiator fan and grille shutters may also cool the exhaust turbine and the exhaust manifold. Thus, durability and integrity of these components may be maintained and/or extended. Overall, degradation of components may be diminished and a decrease in maintenance costs may be provided.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.